In the food or pharmaceutical industries, products or objects such as cans, jars, dishes, bottles, etc. are often sterilized in discontinuous or "batch" autoclaves into which the products to be treated are inserted, the products then being removed after completion of a specified treatment cycle. Such products to be treated are arranged in baskets, on stackable trays, or on other similar storage elements. For certain products, the sterilisation heat treatment should be carried out whilst the product is being stirred inside its packaging. Such stirring is produced inside the autoclave by rotating a drum housing baskets filled with packages containing the products to be sterilised. The same type of problem is posed when certain products are to be drained or tipped up in apparatus other than an autoclave, such apparatus therefore being called a drainer or tipper. This operation allows water deposited on the products to be removed by gravity during sterilisation.
An example of such a rotating drum sterilisation autoclave is described in detail in French patent no. 8602046.
As the drum rotates, it is necessary to avoid any movement of the packages which could cause them to be damaged or destroyed, by immobilizing the packages inside the drum using a specific supporting system. The individual product packages are usually stacked in boxes or placed in trays or racks, and it is the set of these boxes or similar which must be supported inside the drum.
To simplify the following description and claims, any package of a product to be sterilized will be designated generally as an "object".
In order to keep objects stacked inside a rotating drum in place, it has already been proposed, as in French patent application FR-A-2 605 226, to control the support plates for the objects by means of single-acting actuators disposed in the upper part of the drum and acting perpendicularly on the support plates. Such a solution certainly allows the objects to be held inside the drum without manual intervention, but it is unsatisfactory insofar as the single-acting actuators require associated return springs to allow removal of the support plates. Moreover, the actuator rods are connected directly to the presser plates, thereby limiting their stroke and requiring the use of actuators of a particular type because of the lack of space.
It has also been proposed in U.S. Pat. No. 2,629,312 to support objects inside a rotating drum using mechanisms for moving a presser plate, such a mechanism being manually operated by means of a handle and being disposed in the top of the drum. That solution is less than satisfactory insofar as the environment in which intervention is required is hostile, and insofar as manual intervention does not permit an automatic object treatment line to be set up.
Moreover, and most significantly, in all the proposed solutions, the mechanisms for pressing the plates are disposed in the upper part of the drum. That solution permits only limited travel of the plate and also, because of the small space available, does not allow the plates to be uniformly clamped.